a) Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing a wiring structure, more specifically, to a method of manufacturing a wiring structure having an upper wiring layer and lower conductive regions connected via contact holes formed in an insulating layer, and a semiconductor.
b) Description of the Related Art
It is known that a barrier metal layer formed between a semiconductor substrate and a wiring layer of a semiconductor integrated circuit prevents reactions between the substrate and the wiring layer from occurring and enables a stable electric connection. Laid-open Japanese patent application No. 4-214653 discloses a barrier metal layer comprising a titanium layer and a titanium oxynitride layer. The titanium layer reduces the contact resistance between the semiconductor substrate and the wiring layer. The titanium oxynitride layer prevents reactions between the semiconductor substrate and the wiring layer from occurring.
Laid-open Japanese patent application Nos. 5-6865 and 5-121356 disclose a trilayer barrier metal consisting of a titanium layer, a titanium nitride layer and a titanium oxynitride layer. The titanium oxynitride layer is formed by oxidizing the titanium nitride layer.
In this specification, the ratio of O to N in the titanium oxynitride (TiON) layer is not limited to a 1 to 1 ratio. TiO.sub.x N.sub.1-x (x is approximately 0.1) is usual composition of a titanium nitride layer used as a barrier metal. The value of x varies depending on the amount of additive O.sub.2 during the sputtering for deposition.
Such a bilayer structure of a barrier metal layer having a titanium oxynitride layer deposited on a titanium layer has been used conventionally. However, an experiment carried out by the inventors of the present invention proved that such structure hardly shows good electric contact.